Today, there are more and more satellite constellations in LEO. Dozens and hundreds of small satellites are launched for communications, Earth observation, internet services, and scientific research. However, the constellation management costs also increase.
It is becoming increasingly important for operators not only to launch satellites into orbit but also to ensure their operations are cost-effective. The price of the launch, satellite preparation, orbital manoeuvres, constellation maintenance, and safe deorbiting has to be taken into account.
The propulsion system is no longer just an engineering decision, but an economic one. The propulsion system affects not only the satellite’s capabilities but also the total cost of constellation management. The type of propulsion system determines the complexity of integration, safety requirements, launch preparation time, and the costs of subsequent satellite operations.
For a long time, electric propulsion was a default “advanced” solution in the space industry. Although this approach seems more like an expensive overengineering exercise for many LEO constellations.
Why Constellation Management Costs Are Increasing
Not only do launches happen more often, but LEO satellites also have limited service life. Thus, operators have to regularly launch new ones into orbit. This trend puts additional strain on satellite preparation, integration, and constellation management processes. On top of that, operators have to implement additional initiatives for decreasing space debris and safe deorbiting to comply with new space sustainability requirements.
The Hidden Operational Costs
Often, the main expenses are not connected to the launch itself. Once in orbit, a long operational phase begins, which requires ongoing costs.
One of the important goals is orbit maintenance. For this purpose, satellites regularly perform correctional manoeuvres. On top of that, there is also a growing need for collision avoidance manoeuvres. Orbits become more and more crowded, hence satellites have to change their trajectories to avoid collision and space debris.
End-of-life deorbiting is yet another major task. It is necessary to comply with current zero-debris mandates.
Moreover, operators have to manage satellite constellations. It requires infrastructure, automation, and constant monitoring.
Why Propulsion Choices Matter Economically
Commonly, the discussion on propulsion systems is focused on physics metrics rather than business metrics. However, high Isp does not generate revenue. What really matters are reliable deployment, operational simplicity, and manageable lifecycle costs. Electric propulsion is efficient, but it possesses high hidden costs in infrastructure and logistics.
For example, it is possible to estimate the “Xenon/EP Premium”, the additional capital and operational expenditure (CAPEX and OPEX), and compare it to water-based systems like SteamJet. Additional costs in EUR (€) for a typical 3U–12U CubeSat constellation may be estimated based on current market data and aerospace cost-estimation models.
1. CAPEX: Hardware & Integration Premium
High-efficiency EP systems (Ion, Hall, FEEP) are significantly more complex than water-based electrothermal systems.
- Thruster Unit & PPU: A space-qualified FEEP or Ion thruster typically starts at €40,000 to €80,000 per unit. A water-based thruster (electrothermal) generally ranges from €30,000 to €50,000.
Additional Cost: +€10,000 to +€30,000 per satellite. - Power System Sizing (EPS): EP systems often require 40W–100W of peak power, necessitating larger deployable solar arrays and higher-capacity batteries. For a CubeSat, upgrading these components adds roughly €5,000 to €12,000.
- EMI & Integration Testing: EP systems use high-voltage (kV) power processing units, which require rigorous Electromagnetic Interference (EMI) testing to ensure they don’t fry the satellite’s radio or sensors.
Additional Testing Cost: +€5,000 to +€10,000.
2. Propellant & Logistics Premium
While water is virtually free and can be handled in a standard laboratory environment, EP propellants (specifically Xenon) are a major budget line item.
- Xenon Propellant: Current European prices for high-purity Xenon (March 2025 data) are approximately €1,950 per kg. For a small constellation fleet requiring 20kg of Xenon, this is an immediate €39,000 propellant cost. Water costs €0.
- Specialised Fueling: Xenon requires high-pressure ground support equipment and certified technicians.
Additional Handling Cost: +€2,000 to +€5,000 per launch.
3. OPEX: Operational & Monitoring Premium
The hidden costs then are amplified by the “low-thrust” nature of EP.
- Collision Avoidance Manoeuvre Planning: Because EP provides very low thrust (micro-Newtons), collision avoidance must be planned days in advance. This requires higher-fidelity tracking data and more “man-hours” for ground-segment automation and mission analysis.
Additional Labor Cost: Estimated +€2,000 to +€4,000 per satellite/year. - End-of-Life (Deorbiting) Duration: A water-based system can perform a high-thrust “deorbit pulse” to drop perigee quickly. EP systems may take months to spiral down, during which time the satellite must be actively monitored and tracked to comply with “Zero Debris” mandates.
Extended Monitoring Cost: +€1,500 to +€3,000 per satellite.
When talking about satellite constellations, all these costs accumulate very fast. What may seem like an efficient propulsion solution in reality turns out to be a financial problem.
Financial Summary: EP vs. Water Propulsion
Cost Category | Estimated Additional Cost for EP (per satellite) |
|---|---|
Hardware & Power (CAPEX) | €10,000 – €30,000 |
Propellant (Xenon 1kg benchmark) | €2,000 – €3,000 |
Testing & Integration | €5,000 – €10,000 |
Operations & Monitoring (OPEX) | €3,500 – €7,000 / year |
TOTAL INITIAL PREMIUM | ~€20,500 – €50,000 |
For a 10-satellite constellation, choosing Electric Propulsion instead of water could increase the budget by €205,000 to €500,000, plus ongoing operational premiums. For many LEO missions, it is no longer a question if water propulsion is technically suitable. The real question is how long operators can justify paying the electric propulsion premium.
Water Propulsion and Space Sustainability
Space sustainability is a vital part of constellation management. The more satellites are launched into orbit, the higher the risks of collisions and space debris.
Water propulsion helps operators with:
- end-of-life deorbiting
- decrease space debris
- meet current debris mitigation requirements
- enable safer management of large satellite constellations
It is crucial for LEO constellations, where even a few uncontrolled satellites may pose problems to the entire orbital infrastructure. Besides, preventing problems is cheaper than dealing with their consequences. Collisions, satellite loss, and emergency manoeuvres result in additional costs and risks for the mission.
That is why water propulsion helps not only to increase the safety of the mission, but also to decrease long-term operational costs of satellite constellation management.
About SteamJet Space Systems
SteamJet Space Systems is a leading UK-based provider of high-performance satellite propulsion solutions. We specialise in water-based thrusters designed specifically for CubeSats and Small Satellites (SmallSats), with a strong focus on water-based thruster safety.
By pioneering the use of green propellants and intelligent thermal engineering, SteamJet enables complex LEO (Low Earth Orbit) manoeuvres — including orbital maintenance, collision avoidance, and de-orbiting — without the risks associated with toxic hydrazine or high-pressure cold gas systems, advancing green propulsion for space missions.
Steamjet Propulsion Technology
Our modular systems are engineered for seamless integration and maximum safety compliance:
Steam TunaCan Thruster: A compact, high-efficiency solution for 1U-3U CubeSats.
Steam TunaTank Thruster: A safe, high-performance electrothermal propulsion system.
Steam Thruster One: Scalable propulsion for larger SmallSat constellations.
Discover how SteamJet’s sustainable space propulsion innovations are providing the safety and reliability required for the next generation of crewed and robotic missions. Contact our engineering team for technical specifications and ICDs.
